[Clang Interpreter] Initial patch for the constexpr interpreter

Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 370584

1 files changed, 48 insertions, 0 deletions

diff --git a/clang/lib/AST/Interp/Function.cpp b/clang/lib/AST/Interp/Function.cpp
new file mode 100644
index 00000000000..0ed13a92aa3
--- /dev/null
+++ b/clang/lib/AST/Interp/Function.cpp
@@ -0,0 +1,48 @@
+//===--- Function.h - Bytecode function for the VM --------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "Function.h"
+#include "Program.h"
+#include "Opcode.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclCXX.h"
+
+using namespace clang;
+using namespace clang::interp;
+
+Function::Function(Program &P, const FunctionDecl *F, unsigned ArgSize,
+                   llvm::SmallVector<PrimType, 8> &&ParamTypes,
+                   llvm::DenseMap<unsigned, ParamDescriptor> &&Params)
+    : P(P), Loc(F->getBeginLoc()), F(F), ArgSize(ArgSize),
+      ParamTypes(std::move(ParamTypes)), Params(std::move(Params)) {}
+
+CodePtr Function::getCodeBegin() const { return Code.data(); }
+
+CodePtr Function::getCodeEnd() const { return Code.data() + Code.size(); }
+
+Function::ParamDescriptor Function::getParamDescriptor(unsigned Offset) const {
+  auto It = Params.find(Offset);
+  assert(It != Params.end() && "Invalid parameter offset");
+  return It->second;
+}
+
+SourceInfo Function::getSource(CodePtr PC) const {
+  unsigned Offset = PC - getCodeBegin();
+  using Elem = std::pair<unsigned, SourceInfo>;
+  auto It = std::lower_bound(SrcMap.begin(), SrcMap.end(), Elem{Offset, {}},
+                             [](Elem A, Elem B) { return A.first < B.first; });
+  if (It == SrcMap.end() || It->first != Offset)
+    llvm::report_fatal_error("missing source location");
+  return It->second;
+}
+
+bool Function::isVirtual() const {
+  if (auto *M = dyn_cast<CXXMethodDecl>(F))
+    return M->isVirtual();
+  return false;
+}